Orthopaedic surgical skills are largely acquired through apprenticeship in the operating room (OR). This expensive and unforgiving training model struggles to ensure patient safety. The long-term goal of this work is to improve patient safety and outcomes by providing effective simulation tools. The work is significant in that it will provide rigorous scientific evidence that a surgical simulator can improve an orthopaedic resident's OR performance. A common and important skill that orthopaedic residents learn is to drive a sharpened stainless steel pin along a precise path within bone. This task, commonly called wire navigation, is a part of treating many common fractures. The task requires surgeons to rely on 2D fluoroscopic imaging to assess progress of the wire within the bone. Precisely controlling the position of the wire is critical to patient safety and fixation strength. A simulator has been developed to mimic wire navigation in one of the most common surgeries in orthopaedics: the fixing of a fracture of the proximal femur. The augmented reality simulator blends a real drill and surrogate femur with computer-generated fluoroscopic images. The simulator closely replicates the sensation of drilling in the OR while retaining the benefit of a radiation-free training environment. Task performance is assessed upon completion by measuring several important quantities, which can likewise be directly measured in the OR. The specific objective of the proposed research is to measure the effectiveness of using the new simulator to train residents in wire navigation. The central hypothesis is that the simulator reproduces critical elements of actual wire navigation. The following aims will be pursued. Aim 1: Demonstrate how deliberate practice improves wire navigation performance. Multi-institutional studies involving nearly 300 orthopaedic residents will be undertaken to measure the learning curve for acquiring wire navigation skill on the radiation-free simulator. Prior to progressing to the OR, studies will be conducted to show that simulator performance improves performance on a surgical simulation involving actual fluoroscopy. Aim 2: Show that simulator performance correlates with performance in the OR. Additional studies will be conducted to demonstrate that skill assessments with the simulator distinguish junior orthopaedic residents from senior residents. Additional studies will be conducted to determine if performance on the simulator correlates with OR performance. The proposed series of studies link training and assessment in the skills lab to performance in the OR. This paves the way for developing, testing, and improving simulators within orthopaedic surgery. An experienced research team has been assembled, and a commercial partner is ready to foster wider dissemination of the simulator. Increased resident skill in wire navigation gained outside of the OR will spare patients unnecessary additional risk, lead to faster procedures, yield better surgical results, and ultimately provide better patient outcomes.